JP2772107B2 - Power steering control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention is provided in connection with a booster that provides an assist force, and detects an applied current calculated based on a running state such as a vehicle speed, a steering angle, and a steering wheel torque. The present invention relates to a control device for a power steering device including a control device for controlling an assisting force by a booster in response.

(Prior Art) For example, in a control device of a hydraulic power steering device,
It is known to control a steering torque of a power steering device by applying a control current according to a vehicle speed, a steering angle, or the like to an electromagnetic control valve of a control device. According to this technique, satisfactory results can be obtained with respect to the characteristics when the steering wheel is turned, but there is a problem that the steering wheel is felt heavy when the steering wheel is returned or the steering wheel is held.

In order to solve this, in the technology of Japanese Patent Application Laid-Open No. 62-279170, a power steering device having a steering force control device using a reaction force mechanism detects that a steering angle is changing in a direction approaching a neutral position. In response to the output of the return determination means, the current applied to the electromagnetic control valve is reduced and the hydraulic pressure supplied to the reaction force mechanism is increased, so that the return of the steering wheel can be felt well. .

(Problems to be Solved by the Invention) However, in such a technique, a small angle as shown in FIG. 7A is used for correction while the steering wheel is being turned so as to travel a curve or a corner. 7B is repeated, the current applied to the electromagnetic control valve changes each time the control is repeated, as shown by the broken line in FIG. 7B, and the steering wheel torque also changes. .

An object of the present invention is to eliminate the strange feeling by maintaining the applied current in a cutting state until the steering wheel reaches a predetermined angle from the start of its return.

(Means for Solving the Problems) For this purpose, as shown in FIG. 1, a control device for a power steering device according to the present invention includes a steering wheel 46 that steers a steered wheel via an operating member 11, and A booster 12 that applies an assisting force to the operating member 11, a controller 15 that controls the booster 12 to generate an assisting force corresponding to a torque applied to the steering wheel 46, and In a power steering device including a calculation output means 2 for calculating an applied current and outputting the calculated current to the control device 15 to change the assist force, a steering angle sensor 45 for detecting a steering angle of the steering wheel 46; Return determination means 1 for detecting a steering wheel return state based on a change in the steering angle detected by the steering angle sensor 45; and a return angle of the steering wheel 46 detected by the steering angle sensor 45 to determine the return. After reaching a predetermined angle from the start of the detection of the return state of the steering wheel by step 1, the assist force acting on the direction of the torque applied to the steering wheel 46 by the applied current calculated by the calculation output means 2 is reduced. Characterized in that it is provided with an additional calculating means 3 for changing to.

(Operation) At the time of turning the steering wheel, an applied current corresponding to the running state of the vehicle of the calculation output means 2 is calculated and output to the control device 15, whereby the power booster 12 applies an assist force to the operating member 11 to perform power steering. Done. When the return determination means 1 determines that the steering wheel is in the return state, the calculation output means 2 similarly calculates an applied current corresponding to the running state of the vehicle, and the additional calculation means 3 uses the steering angle sensor 45 to calculate the applied current. The detected return angle of the steering wheel 46 is output to the control device 15 as it is from the start of the detection of the steering wheel return state by the return determination means 1 until the predetermined angle is reached, and is added to the steering wheel 46 after reaching the predetermined angle. The control device 15 is changed by changing the assist force acting on the direction of the torque so as to decrease.
Output to Thus, the assisting force by the booster 12 when the steering wheel returns is the same as when the steering wheel is turned until the steering wheel reaches the predetermined angle from the start of the return.

(Effects of the Invention) As described above, according to the present invention, the applied current is the same as when turning the steering wheel 46 until the steering wheel 46 returns to the predetermined angle from the start of the steering wheel 46. The assist force does not change even if the steering wheel is returned and the incision is repeated, so that the steering does not give a feeling of strangeness. If the steering wheel return angle exceeds a predetermined angle, the applied current is given by the increment device and changes in a direction in which the assist force acting on the direction of the torque applied to the steering wheel decreases, and the steering wheel torque is reduced. Change to a direction that feels good.

(Example) Hereinafter, the present invention will be described with reference to an example shown in Figs. 1 to 7.

As shown in FIGS. 1 and 2, the power steering device 10
A power cylinder (power booster) 12 provided on an operating rod (working member) 11 connected to a steering wheel (not shown) via a steering link mechanism, and a control device 15.
It comprises a rack / pinion mechanism 13, a servo valve 17 provided on a rotating shaft 16 connecting the operating rod 11 and the steering handle 46 via a handle shaft 47, and a reaction force mechanism 18 having an electromagnetic control valve 30.

A supply pump 20 such as a vane pump driven by an automobile engine has a built-in bypass valve 21, whereby a working fluid having a constant flow rate Q is supplied to a flow dividing valve 22 through a discharge passage 23. The flow dividing valve 22 distributes a constant flow rate Q of the working fluid to the servo valve passage 23a and the reaction force control passage 23b by constant flow rates Q1 and Q2, respectively. The servo valve passage 23a is connected to the power cylinder 12 through the servo valve 17, and the reaction force control passage 23
The reaction force mechanism 18 and the electromagnetic control valve 30 are connected to b.
When an electric pump is used as the supply pump 20, the bypass valve 21 is unnecessary.

The servo valve 17 is a known rotary type open center type 4-port throttle switching valve, and is operated by the twist of the rotating shaft 16 (a torsion bar is provided at an intermediate portion) based on the steering wheel torque applied to the steering wheel 46. The aperture between the ports 18a to 18d is controlled. In the neutral steering state where steering wheel torque does not occur, the servo valve 17
Since both distribution ports 17c and 17d have the same low pressure, the power cylinder 12 is not operated. If the steering wheel 46 is turned to one side to generate a steering wheel torque, the servo valve 17 is deviated from the neutral state, and the gear generation pressure of the working fluid from the supply port 17a increases, and the one distribution port 17c (or 17d)
Flows into one working chamber of the power cylinder 12 through one distribution passage 24a (or 24b) to generate an assist force, and the working fluid in the other working chamber is supplied to the other distribution passage 24b.
(Or 24a) to the other distribution port 17b (or 17c)
And discharged to the reservoir 25 through the discharge port 17b. The steering force acting on the operating rod 11 is increased by the assist force, and is transmitted to the steered wheels via a steering link mechanism (not shown).

The reaction mechanism 18 has an insertion hole 18 formed on the output side of the rotating shaft 16.
and a plunger 18b fitted to c and an inclined surface 18d formed on the input side of the rotating shaft 16 and inclined on both sides in the circumferential direction to be engaged with the tip of the plunger 18b. . Then, the pressure of the working fluid introduced into the rear part of the plunger 18b through the port 18a is changed by the electromagnetic control valve 30 to change the torsion spring characteristic between the input and output sides of the rotary shaft 16, thereby changing the power cylinder 12 This is to change the operation characteristics of the servo valve 17 that controls the supply and discharge of the working fluid to both working chambers. The electromagnetic control valve 30 is normally fully closed,
The opening increases in accordance with the increase in the current applied to the solenoid 30a, and finally opens fully.

As shown in FIG. 2, the electronic control unit 50 includes a central processing unit (hereinafter simply referred to as a CPU) 51, a read-only memory (hereinafter simply referred to as a ROM) 52, and a writable memory (hereinafter simply referred to as a RAM).
53 is a main component, and the CPU 51 is connected to a solenoid 30a of the electromagnetic control valve 30 via an interface (not shown) and a solenoid drive circuit so as to control an applied current. The CPU 51 has a vehicle speed sensor 40 and a steering angle sensor 45 via an interface (not shown).
And a timer 48 are connected. The steering angle sensor 45 is provided on the handle shaft 47, detects a steering angle θ of the steering wheel 46 of the steering wheel 46 by generating a steering angle pulse for each predetermined small steering angle, and the vehicle speed sensor 40 is an engine. Output shaft of transmission 42 that transmits 41 driving force to rear wheels
43 is provided to detect the vehicle speed v. Timer 48
Is reset each time the steering angle sensor 45 generates a steering angle pulse and starts timing.

In the ROM 52, the vehicle speed v, the steering angle θ, and the steering angular speed dθ / dt of the applied current I output to the solenoid 30a of the electromagnetic control valve 30 are stored.
Are stored. The characteristics of the applied current I include the characteristics of the base current I ₀ , the characteristics of the correction current i _{1, and the} characteristics of the first to third correction coefficients k ₁ , k ₂ , and k ₃ . This is shown in the figure as a characteristic map.

Base current I _0, as shown in the FIG. 4 (a) and (b), it changes so as to decrease from the value relative to the increase in the absolute value of the vehicle speed v and the steering angle theta. In the prior art without special control when returning the steering wheel, this base current
Only I ₀ is applied to the electromagnetic control valve 30, in this case handle returned is felt heavier.

The first correction current i ₁ is, as shown in FIG.
It is 0 up to a certain value, then rapidly increases, returns to 0 in two steps, and changes to 0 thereafter. The second correction current i ₂ as shown in FIG. 5 (b), until the first correction current i ₁ becomes 0 is 0, then increases to a certain value promptly in response to an increase in the vehicle speed It changes to be kept at that value. The first correction coefficient k ₁ as shown in Figure No. 6 (a), a 0 gradually decreases to the value in with increasing steering angle theta. The second correction coefficient k ₂ is held in the sixth as shown in Figure (b), the value increases to rapidly value from 0 with increasing steering angle velocity d [theta] / dt. The third correction factor k ₃ as shown in Figure No. 6 (c), but up to a certain value with an increase in the steering angle θ is 0 is held increases to a certain value then promptly on that value. As described later, the first correction current i ₁ , the first correction coefficient k _1, and the second correction coefficient k ₂ are employed in a low-speed traveling state, and the second correction current i ₂ and the third correction coefficient k ₃ Is used in a medium to high speed running state. In the present embodiment, each of these characteristics is
2 is stored as a characteristic map, but may be stored as an empirical formula or a functional formula.

The ROM 52 stores a control program for calculating the return angle of the steering angle θ from an arbitrary maximum position as shown in FIG. 7A. This return angle is obtained by counting the number of steering pulses from the steering angle sensor 45 since the steering wheel return flag F described below becomes 1.

Further, the ROM 52 stores a control program that sets the steering wheel return flag F to 1 when the value of the steering angular velocity dθ / dt calculated based on the steering angle θ that changes every moment is negative (that is, in the return state). Furthermore the ROM 52, the vehicle speed v, the base current I ₀ from the characteristics of FIG. 4-FIG. 6 based on the steering angle θ and the steering angular velocity d [theta] / dt, the first correction current i _1, the second correction current
i _{2 and the} first to third correction coefficients k ₁ , k ₂ , k ₃ are calculated, and in the case of low-speed running, when F = 1 and F = 1 and the aforementioned steering wheel return angle is a predetermined angle When it is smaller than α, an applied current of I = I ₀ is output to the electromagnetic control valve 30, and when F = 1 and the steering wheel return angle exceeds a predetermined angle α, I = I ₀ −i ₁ × k ₁ It applied when × a k ₂ becomes the applied current I is output to the solenoid control valve 30, in the case of medium and high speed running is also the time measured by and timer 48 instead of F = 1 does not exceed the predetermined time T ₂ Control to gradually decrease the applied current I output to the electromagnetic control valve 30 until the current I becomes the base current I _0, and otherwise to gradually reduce the applied current I until I = I ₀ + i ₂ × k ₃ A program is stored.

Next, the control operation of the above embodiment will be described with reference to the flowchart of FIG.

When the main switch of the car is turned on, the electronic control unit 50
Sets each variable to 0 or a predetermined initial value. The vehicle speed v and the steering angle θ that change every moment in the running state of the vehicle
Are detected by the vehicle speed sensor 40 and the steering angle sensor 45, and their current values are input to a register (not shown). CPU51
Is a handle return flag F based on a control program (not shown).
Is calculated, and the processing operation is executed based on the control program shown in the flowchart of FIG.

The CPU 51 first proceeds to step 101 in the flowchart of FIG.
In, after reading the current vehicle speed v and the steering angle θ stored in the register, it calculates the base current I ₀ based on the vehicle speed v and the steering angle θ by each characteristic map stored in step 102 to the ROM 52. In the following step 103, C
PU51 compares the vehicle speed v and the predetermined value V _1, if v <V ₁ (if low speed) returns advances the control operation of the control 110,
v <(if it is a medium or high speed running) V ₁ unless Hokajiryoku control 22
The control operation proceeds to 0.

In the return control 110 which is a main part of the present invention, first, step 1
F is not 1 which is separately calculated in 11, i.e. if not handle return state, CPU 51 has the applied current I and I ₀ in step 114, in step 120 outputs the applied current I to the solenoid 30a of the solenoid control valve 30. As a result, the steering wheel torque in the steering wheel cut state becomes the same value as in the related art.

If F = 1 in step 111, that is, if the steering wheel is in the returning state, the CPU 51 advances the control operation to step 112, and the steering wheel returning angle from the maximum position of the steering angle θ immediately before that (separate calculation as described above) is a predetermined angle. It is determined whether it is equal to or more than α. If the angle is not greater than the predetermined angle α, the CPU 51
Advances the control operation to step 114 to perform the same control as described above, and if so, advances the control operation to step 113,
Calculated from the previously calculated base current I ₀ and each characteristic map
The applied current I is calculated by i ₁ , k ₁ , k ₂ and the following equation I = I ₀ −i ₁ × k ₁ × k _{2, and the} reduced applied current I is calculated in step 105 by the solenoid 30a of the electromagnetic control valve 30.
Output to That is, the steering wheel return angle is a predetermined angle α.
Until the above, the steering wheel torque is the same as the steering wheel cut state. When the steering wheel torque exceeds a predetermined angle α, the assisting force in the steering wheel returning direction is reduced, and the steering wheel returning at the time of low-speed running becomes good.

The assist force acts in the same direction as the steering wheel torque applied to the steering wheel 46 (direction that assists the steering wheel torque) to reduce the steering wheel torque.
The direction of this steering wheel torque is the turning direction when the steering wheel is turned and the steering wheel is held against the return of the steering wheel, and the steering wheel is returned faster than the free steering wheel return speed. In the state where it is in the return direction. Therefore, as described above, the assisting force in the steering wheel return direction decreases when the steering wheel return angle becomes equal to or larger than the predetermined angle α in the steering wheel return state during low-speed running.

Also, in the context of the claims, the program for executing the return control in the flowchart shown in FIG. 3 changes the arithmetic output means 2 and the step 113 and its related parts change the additional arithmetic means 3 every moment. When the value of the steering angular velocity dθ / dt calculated based on the steering angle θ is negative (that is, in the return state), the program for setting the steering wheel return flag F to 1 constitutes the determination means 1, and all of them constitute the determination means 1.
It is stored in the ROM 52.

FIG. 8 is a flowchart showing an example of the prior art (not known) of the applicant. According to the return control 210, a small angle is set for correction while the steering wheel cutting operation is being performed. When the return of the steering wheel and the incision are repeated, the current applied to the electromagnetic control valve changes each time the repetition is performed as shown by the broken line in FIG. 7 (b), whereby the steering wheel torque also changes. However, in the above-described embodiment, even if the return of the steering wheel and the incision are repeated within the range of the predetermined angle α, there is no strange feeling as in the related art.

V unless <V ₁ at step 103, CPU 51 computes the applied current I running control operation shown in fixed steering force control 220, and outputs this to the solenoid 30a of the solenoid control valve 30 at step 105. In this case, after the time t ₂ measured by the timer 48 has passed the predetermined time T ₂ , the applied current I when returning the steering wheel gradually increases as compared with when turning the steering wheel. Steering when returning the steering wheel can be felt lightly. Since the steering force control 220 is not a main part of the present invention, only a flowchart is shown and a detailed description is omitted.

When step 105 ends, the CPU 51 temporarily stops executing the processing operation according to the flowchart in FIG. Thereafter, each time the interrupt signal is output at predetermined small time intervals, the CPU 51 repeatedly executes the processing operation according to the flowchart of FIG. 3 to determine the vehicle speed v, the steering angle θ, whether the steering wheel is turned or returned, and the steering wheel return angle. The applied current I calculated according to the above is output to the solenoid 30a of the electromagnetic control valve 30 to control the steering wheel torque.

In the present embodiment, when the steering wheel return angle exceeds a predetermined angle α during low-speed running, the applied current I is suddenly reduced as shown by the solid line in FIG. Is suddenly reduced, but the opening degree of the electromagnetic control valve 30 may be gradually reduced after the applied current I is changed to exceed the angle α as shown by a two-dot chain line in FIG.

In the above embodiment, the case where the reaction force type steering force control device is used has been described.However, the present invention bypasses between the two distribution ports 17c and 17d of the servo valve 17 or between the discharge side and the suction side of the pump. The present invention can also be implemented in a system using a bypass-type steering force control device provided with an electromagnetic control valve.
Further, in this embodiment, the steering wheel return flag F is determined by the steering angle sensor 45, but the determination may be performed by the steering angle sensor and the torque sensor that detects the steering wheel torque.
Further, each characteristic map may be changed stepwise instead of changing continuously as in the embodiment.

The present invention can also be implemented in an electric power steering device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a control device of a power steering device according to the present invention, FIGS. 2 to 7 show an embodiment of the present invention, FIG. 2 is an overall explanatory diagram, and FIG. FIG. 4 is a characteristic diagram of the base current, FIG. 5 is a characteristic diagram of each correction current, FIG. 6 is a characteristic diagram of each correction coefficient, and FIG. 7 is a change in the steering angle and applied current with respect to time. It is a figure showing a state. FIG. 8 is a flowchart of a control program of the prior art by the applicant. DESCRIPTION OF SYMBOLS 1 ... Return judgment means, 2 ... Calculation output means, 3 ... Additional calculation means, 11 ... Working member (Working rod), 12 ... Strengthening device (Power cylinder), 15 ... Control device, 16 ... rotating shaft, 45 ... steering angle sensor, 46 ... steering wheel.

Continuing on the front page (72) Inventor Yoshiyuki Shibata 1-1, Asahi-cho, Kariya-shi, Aichi Prefecture Inside Toyota Koki Co., Ltd. 72) Inventor Yuzo Kubota 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-3-109171 (JP, A) JP-A-3-112778 (JP, A) JP-A Sho 61-295172 (JP, A) JP-A-1-175569 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 6/00

Claims (1)

(57) [Claims] A steering wheel for steering a steered wheel via an operating member; an intensifier for applying an assist force to the operating member; and the booster for generating an assisting force corresponding to a torque applied to the steering handle. A power steering device comprising: a control device that controls the device; and a calculation output unit that calculates an applied current according to a running state of the vehicle and outputs the calculated current to the control device to change the assist force. A steering angle sensor for detecting a steering angle of a steering wheel, return determination means for detecting a steering wheel return state based on a change in the steering angle detected by the steering angle sensor, and a return of the steering wheel detected by the steering angle sensor After the angle reaches a predetermined angle from the start of detection of the steering wheel return state by the return determination means, the applied current calculated by the calculation output means is Control device for a power steering apparatus, characterized in that the assist force acting in the direction of the torque applied to the steering handle is provided with an additional operating means for varying so as to reduce.